Process for drying photographic emulsions



Dec. 2, 1952 C. E. ROSE PROCESS FOR DRYING PHOTOGRAPHIC EMULSIONS FiledJuly 18. 1951 2 SHEETS-SHEET l N www@ lnl Hf od l* N" ,iN s SN IN V ENTOR. C/ze5 ef'lfzge rielase A T TORNE Y.

DCC. 2, 1952 C, E ROSE 2,620,285

PROCESS FOR DRYING PHOTOGRAPHIC EMULSIONS Filed July 18, 1951 2 SHEETS-SHEET 2 DKYIN' G CHAJYEBE'R CSEASo/WNG CHAMBER IN VEN TOR.

Chestefgezeose A TTORNE Y.

Patented Dec. 2, 1952 PROCESS FOR DRYING PHOTOGRAPHIC EMULSIONS ChesterEugene Rose, Raritan Township, Middlesex County, N. J., assigner to E.I. du Pont de Nemours & Company, Wilmington, Del., a. corporation ofDelaware Application July 18, 1951, Serial No. 237,418

8 Claims.

This invention relates to a process for setting and drying photographicsilver halide emulsion coatings. More particularlyv it relates to acontinuous process of setting and drying gelatino silver halide emulsioncoatings on continuous supports such as flexible films or papers.

The manufacture of photographic films and papers includes the steps ofdepositing a coating of warm, owable colloid silver halide emulsion ontoa support, the cooling of the liquid emulsion layer below its settingpoint to form a gelled layer, and drying to remove excess water. Thesetting` is accomplished by passing the support after coating into achilled zone. After the emulsion is set, it is then dried. The dryingoperation must be conducted under such conditions that the emulsionlayer is not remelted. The conventional methods of drying aretime-consuming and require large buildings and apparatus.

An object of this invention is to provide an improved process of settingand drying gelatina silver halide emulsion coatings. A further object isto provide such a process which requires shorter drying period. Arelated object is to provide such a process which can be practiced insmaller apparatus and buildings. A still further object is to provide arapid process for setting and drying gelatino silver halide emulsionlayers which gives coatings of uniform quality. Still other objects willbe :apparent from the following description.

The above objects are accomplished by the present invention which in itsbroader aspects consists in passing the support, e. g., film or paper,after it has been coated with an aqueous gelatine silver halide emulsioninto a chilling zone that is maintained at a temperature below '75 F.,preferably at 40 to 70 F. depending upon the gelatin content, wherebythe Iemulsion is firmly and smoothly gelled. Low gelatin contentemulsions require the lower temperatures. The element is then passedinto a conditioning zone which is maintained yat a temperature which isfrom 5D to 30 F. bel-ow the melting point of the gelatine silver halideemulsion layer for la period of about i0 to 180 seconds whereby a rmergel is formed. The element is then passed into a drying Zone and thelayer is dried by means `of a high velocity current of air which ismaintained at such a temperature and humidity that the emulsion isabo-ve its normal melting point without the aforementioned conditioning.The element is removed from contact with such air after the moisturecontent of the emulsion has been reduced to produce a water to gelatinratio of 0.5 to 1.5 to 1.0 by weight.

(Cl. 11W-103) The drying conditions may vary widely but a dry-bulbtemperature of 110 to 235 F. :and a wetbulb temperature 2 to 20 F. abovethe normal melting point of the gelled but unconditioned emulsion layerand va period from 30 to 180 sec. is preferably used at an air velocityof 2,000 to 15,000 feet per minute or greater, and the element sodisposed that the emulsion surface is exposed to the current of air. Theconditions 'being such that the rate of evaporation from a free watersurface would be 0.5 to 3.0 lbs. per hour per square foot. The emulsionlayer as it emerges from the high velocity zone has its water contentreduced to the desired level.

It has been found that the emulsion layers and particularly those whichcontain a substantial amount of soluble bromides and chlorides can befurther improved if they are removed from the foregoing treatment whenthe water to gelatin ratio is between 0.5 and 1.5 to 1.0 and passed intoa curing zone where a current of air passes over the surface of theemulsion layer at a velocity of l0 to about 2,000 or more feet perminute at a dry-'bulb temperature of 70 F. to 100 F., a wetbulbtemperature from 50 F. to 75 F. and a relative humidity of 30% to 60%.The conditions being such that the rate of evaporation from a free wetsurface would be less than 0.5 lb. per hour per square foot andpreferably less than 0.2 lb. .per hour per square foot. The emulsionlayer then may be passed through a seasoning zone maintained at a stilllower temperature, were the linal water to gelatin ratio is adjusted tobetween 0.23 and 0.34 to 1.0, prior to being wound` on suitable take-uprolls.

The conditions described above in the first high-velocity,high-temperature drying zone result in an extremely high rate ofevaporation lof the undesired water from the gelled emulsion layer. Therapid rate of evaporation has a cooling effect on the emulsion layer andalthough it exhibits a tendency to melt while in this zone, because thewet-bulb temperature of the air is suc that the emulsion layer is aboveits normal melting point, the previous conditioning at approximately F.permits the use of high temperatu'res without any significant melting ofthe emulsion.

It has been found that if the passage of the gelled emulsion layerthrough the high-temperature, high-velocity drying zone is controlled soapproximately to 95% of the water content of the Ioriginal liquidemulsion has been evaporated to produce a water to gelatin ratio of between 0.5 and 1.5 to 1.0 by weight, the physical and photographicproperties of the layers are 3 quite satisfactory and the rapidconcentration of the soluble salts in the emulsion is notdisadvantageous. The residual water is then removed in the curing zoneand equilibrium is brought about in the seasoning zone or chamber.

Suitable apparatus for carrying out the process described above aredisclosed in the accompanying drawing which forms a part of thisspecincation. Referring now to the drawing:

Fig. 1 is an elevation of a suitable apparatus for carrying out theprocess;

Fig. l-A is a section taken along the line A-A of Fig. 1;

Fig. 2 is an elevation of a modined apparatus for carrying out theprocess;

Fig. 3 is an elevation of another modified apparatus for carrying outthe process; and

Fig. 4 is an elevation of another modined apparatus for carrying out theprocess.

In Figs. 1, 2, 3, and 4 a roll of nlm I passes over guide roller I andunder guide roller 8 into contact with a gelatin silver halide aqueousemulsion in coating pan 6. It then passes into a cooling tower Il overguide roller or drum I3, then into a horizontal chamber and then into ahigh-velocity, high-temperature drying chamber I6 which communicateswith a source of hot air through a plurality of slots or openings. Thenlm then passes to a rewind station.

An elongated slot or outlet I6 (as shown in Figs. 1, 2 and 3) forexhausting the hot air is provided at the sides of the drying chambernear edges of the emulsion surface or the sides may be completely openas shown in Fig. 4. Hot air having a velocity of 2,000 to 15,000 feetper minute and the wet and dry-bulb temperatures and relative humiditydescribed above passes through the drying chamber to the outlets, e. g.,in the sides of the chamber and at the top of the horizontal chamber.

The cooling tower should be of such length that the emulsion gels and isnrmly set and conditioned before it passes into the high-velocity dryingchamber. In general, a unitl foot of nlm should remain in the coolingtower for a period of about one minute and in the high-temperature,high-velocity drying chamber about two minutes.

Referring now to Fig. 4 which illustrates a practical although morecomplex commercial apparatus, a roll of transparent nlm base I is passedover a series of guide rolls 2 and 3, the lower guide rolls 3 beingmounted on a movable frame so that they can move upwardly anddownwardly. The elevator construction just described is cornmon inphotographic processing apparatus and, since it forms no part of thepresent invention, is not shown in detail. The elevator construction,however, permits one t9 start a new roll Iy through the machine withoutinterrupting the continuous coating and drying. The series of guidingrolls 2 and 3 and elevator construction, may be mounted in a chamber 4which can be heated or cooled so that the nlm has a uniform temperatureas it passes into the coating unit 5.

The coating unit includes a coating pan 6 which is continuously suppliedwith an aqueous gelatino silver halide emulsion maintained at a constantlevel. The nlm I passes over guide roller 1 and under guide roller 8disposed in the pan where it comes into contact with the surface of thecoating solution and picks up a thin layer of silver halide emulsion.Ihe coated nlm then passes upwardly through a cooling or setting chamber9 which is maintained at a temperature of 40 to 60 F. by means of coolair which passes from a large plenum chamber I0 through a piurality oforinces or slots so that it sweeps over the emulsion surface as well asthe back of the coated nlm. The nlm then passes through an elongatedconditioning tower I I that is provided at its upper end with a chamberI2 which surrounds it and is provided with communicating orinces orslots. The cool air from the cooling tower passes through said orincesor slots into chamber I2 where it is withdrawn from the system or cooledand recirculated through chamber I0. If cold air is fed to chamber I0 inorder to obtain quick setting, as is desirable for dilute aqueousgelatino silver halide emulsion coating solutions then warmer air isused in tower Il. This warmer air should, however, be 2 F. to 10 F.below the melting point of the coating in order to condition it in asshort a time as possible.

At the top of the tower II there is provided a guide roller or drum anda closely-ntting baille I4 which leaves a narrow opening at the end ofthe tower for the passage of the nlm with its nrmly-set and conditionedgelatino silver halide emulsion layer into horizontal chamber I5, whichin this case is a drying chamber connecting with vertical drying chamberI6. These chambers are provided with a plurality of spaced slots whichcommunicate with large air ducts II and II and- I8 and I8',respectively, whereby warm drying air impinges upon or flows over one orboth surfaces of the coated nlm element. This air is withdrawn at thesides of chamber I6 which are open as shown in Fig. 4 or may haveelongated slots like I6 as shown in Figs. 1, 2 and 3. The air is alsowithdrawn from the sides of chamber I5 which are open or provided withelongated slots disposed parallel to and just above the path of theemulsion surface of the nlm.

The coated nlm then passes over guide roller I9 downwardly throughvertical chamber I6 and under similar guide roller 20 past anotherclosely ntting baille I4' then upwardly through a curved curing Zone 2lin contact with a series of spaced rollers 22 then over roller 23 anddownwardly through a curved curing zone 2|' which communicates freelywith said curing zone 2l. A series of rollers 24 guide the nlm duringits passage through chamber 2l. A series of slots are provided in thewall of the nrst curved section of the curing chamber opposite theemulsion surface of the nlm'which communicate with a large duct 25through which warm air is supplied. This air then passes through thesecond curved chamber 2l and is exhausted through side openings 2l". Theend of this chamber is provided with baffles I4 to prevent passage ofair into seasoning chamber 26. The nlm passes under a roller 21 disposedat the entrance end to chamber 26 and then over a series of upper andlower rollers 28 and 29. A few of such rollers can be provided with anelevator mechanism to permit changing spools 30 without stopping thedryer. The seasoning chamberl 26 has a wet and dry-bulb temperaturelower than those in the previous drying zone and these nnal temperaturesare determined by the desired nnal moisture in the nlm.

It has been found that a gelatino silver halide emulsion which is coatedon a support is adequately conditioned against remelting if it is in theconditioning tower for a period of about 10 to 180 seconds depending onthe gelatin concentration of the emulsion. When the air flows over thewet side only, the element should remain in the high-temperature.high-velocity air drying chambers I and I6 for about 30 to 180 seconds.The dry-bulb temperature should be from 110 F. to 235 F., the Wet-bulbtemperature should be from 68 F. to 100 F., and the dew point from 40 F.to 70 F. The combination of conditions is such that the rate ofevaporation from a free wet surface is 0.5 to 3.0 pounds per hour persquare foot. The film should remain in curing chamber 2| for a period of30 to 1'50 seconds at the lm speed of 20 to 60 feet per minute with thedry-bulb temperature about 75 F. to 90 F. and the wet-bulb temperatureabout 65 F. to 75 F. and the air velocity adjusted to give a rate ofevaporation from a free wet surface of 0.1 to 0.5 pounds per hour persquare foot. The final conditioning zone should be designed so that theunit length of film remains in it from 4 to 12 minutes at a dry-bulbtemperature of 70 F. to 90 F. and a wet-bulb temperature of 60 F. to 75F. a humidity of 30-60% and the air velocity adjusted to give a rate ofevaporation from a free wet surface of 0.1 to 0.3 pounds per hour persquare foot. The inveniton, of course, is not limited to such filmspeeds. To the contrary, the rate of travel may vary over a very widerange, e. g., l0 to 200 feet per minute or more.

The invention will be further illustrated but it is not intended to belimited by the following examples:

Example I A gelatino-silver iodo-bromide emulsion containingapproximately 0.097% silver iodide, 4.903% silver bromide, 6.34% gelatinand 88.66% Water by Weight is coated onto a sheet of cellulose acetatefilm base at the rate of 18 grams of liquid emulsion per sq. ft. Thecoated film is passed into a setting zone and a conditioning zone whereit is subjected to a concurrent stream of air at 60 F. for 130 seconds.It is then passed into the turbulent air drying zone where jets of airat 120 F. dry bulb and 75 F. Wet bulb impinge against the surface at avelocity of 8000 feet per minute for 120 seconds through slots 1%; inchwide extending completely across the film spaced 6 inches apart andspaced 2 to 6 inches from the web. The drying rate was 1.1 pounds ofWater per hour per square foot of free wet surface. The lm next passesinto a curing Zone, having a dry bulb temperature of 85 F., a Wet bulbtemperature of 70 F. and an air velocity of 40 feetA per minute parallelto the surface of the web, for 120 seconds and then passes into aseasoning zone, having a dry bulb temperature 84 F., a wet bulbtemperature of 70 F. and an air velocity of ten feet per minute for 480seconds. The drying rate in the curing zone was 0.02 pound and that inthe seasoning zone 0.01 pound of water per hour per square foot of freeWet surface. At the end of this final period the moisture content of thefilm is 2.48%.

Example II A gelatine-silver halide emulsion containing about 4.7%silver halide, 4.6%v gelatin and 90.7% water by weight is coated onto acellulose acetate film at a rate of- 14.0` grains of liquid emulsion persq. ft. The coated film is passed into a setting and conditioning zonewhere it is subjected to a concurrent stream of air atl 55 F. for 110seconds. It is then passedV into a vturbulent air drying zone where jetsof air at 110 F. dry bulb and 72 F. wet bulby impingev against thesurface at a velocity of 8000 feet per minute for a period of 180seconds through slots T31; inch wide extending completely across thefilm spaced 6 inches apart and spaced 2 to 6 inches from the Web. Thedrying rate was 1.0 pound of water per hour per square foot of free wetsurface. The gelatino silver halide layer was sufficiently dried attheend of this period and the emulsion had a moisture content below2.5%.

Ezvample III A gelatino-silver iodo-bromide emulsion containingapproximately 0.059% silver iodide, 4.64% silver bromide, 4.55% gelatinand 90.8% Water by Weight is coated onto a cellulose acetate film baseat the rate of 13.8 grams per sq. ft. The coated lm is passed into asetting and conditioning zone Where it is subjected to a concurrentstream of air at 55 F. for 110 seconds. It is then passed into theturbulent air drying zone where jets of air at 110 F. dry bulb and 72 F.wet bulb impinge against the surface at a velocity of l3000 feet perminute for a period of 105 seconds through slots inch wide extendingcompletely across the film spaced 6 inches apart and spaced 2 to 6inches from the web. The drying rate was 1.0i pound of water per hourper square foot of free wet surface. It next passes into a curing zone,having a dry bulb temperature of F., a wet bulb temperature of 71 F. andan air velocity of 40 feet per minute parallel to the surface of theweb, for two minutes and passes into a seasoning zone, having a dry bulbtemperature of 84 F., a wet bulb temperature of 70 F. and an airvelocity of ten feet per minute parallel to the surface of the web foreight minutes. At the end of this final period, the moisture content ofthe film is 1.8%. The drying rate in the curing zone was 0.04 pound andthat in the seasoning zone 0.01 pound of water per hour per square footof free wet surface.

Example IV A gelatino-silver bromo-chloride emulsion containingapproximately 1.96% silver bromide, 3.57% silver chloride, 3.92% gelatinand 90.55% water is coated onto a sheet of cellulose acetate lm base atthe rate of 13.6 grams per sq. ft. The coated lm is then passed into asetting and conditioning Zone where it is subjected to a concurrentstream, of air at 40 F. for 180 seconds, then passed into the turbulentair drying zone where jets of air at F. dry bulb and 70 F. wet bulbimpinge against the surface at a velocity of 4200 feet per minute forseconds through slots Tse inch Wide extending completely across the filmspaced 6 inches apart and spaced 2 to 6 inches from the web. The dryingrate Was 0.6 pound of water per square foot of free wet surface. It nextpassed into -a curing zone, having a dry bulb temperature of 85 F., awet bulb temperature of 70 F. and an air velocity of 40 feet per minuteparallel to the surface of the web for two minutes. It next passes intoa seasoning zone, having a dry bulb temperature 82 F., a wet bulbtemperature of 70 F. and an air velocity of ten feet per minute parallelto the surface of the web for eight minutes. At the end of this finalperiod the moisture content of the film is 1.78%. The drying rate in thecuring zone was 0.03 pound and. that in the seasoning zone 0.01 pound ofwater per hour per square foot of free wet surface.

When drying thin reversible colloid layers, it has been found the rateof evaporation depends upon many factors: (l) the air velocity, (2) thelmanner of directing the air against the material,

(3) the temperature of the air, (4) the humidity of the air, the rate atwhich the moisture diffuses through the material. The first four itemsrelate to drying conditions and can be specied or rated by the pounds ofwater which would be evaporated per sq. ft. in one hour from the surfaceof a container `of water or a free wet 'surface Item (5) is a functionof the material being dried, its moisture content and the rate ofdrying.

In describing drying conditions, I prefer to specify them by the amountof water which would be evaporated from a free wet surface. For a givenrate of evaporation the temperature and humidity may be varied over wideranges provided compensating changes are made in air velocity.

Thus in the drying step of the invention e. g., in the rst section ofthe apparatus of Fig. 4 one may use conditions which will produce ratesof evaporation as high as 1.0 to 3.0 lbs. of water per hour per sq. ft.It is in some cases desirable to reduce the drying conditions after 90to 95% of the water has been evaporated. Thus in the case of aqueousgelatino-silver emulsions it is desirable to reduce the dryingconditions when the water content is between 50% and 150% of the gelatincontent. At this point the conditions are changed to give a curingcondition wherein a drying rate from a free wet or water surface of lessthan 0.5 lb. per hour per square foot and preferably less than 0.2 poundper hour per square foot until the water to gelatin ratio reaches avalue between .23 and .34 to 1.0.

Reducing the drying rate as specied above appears to permit theelectrolyte salts present in the emulsion to distribute uniformlythrough the layer and act to conduct away any static electricitygenerated. If the conditions producing high drying rates are continuedthroughout the entire period of drying and curing the electrolytes actas though they were buried below the surface, they will not conduct awaythe static electricity. As a consequence the static builds up until aspark discharge is produced causing static marking of the photographicfilms.

The conditioning step of the invention which takes place immediatelyafter passing through the setting chamber and before the high velocityair drying is an important feature of the invention. The period t ofconditioning before drying may be represented by the following empiricalformula:

(WB-69) C5N3S2 TZJB t=conditioning time in seconds C=percent gelatin inemulsion N :gelatin Viscosity S :gelatin gel strength T=conditioningtemperature-JF. WB=wet bulb temperature in dryer- T.

This equation, while not exact for very dilute or very concentratedaqueous colloid solutions, applies for aqueous colloid concentrationsbetween 4% and 6% gelatin. The formula does, however, indicated thecomplex nature of the operation and how the higher setting temperaturespermit higher drying temperatures.

It is obvious that the process of this invention can be carried out inapparatus which vary considerably from that shown in the accompanyingdrawings. Additional coating units and high- Velocity drying units canbe used in series to coat a plurality of gelatin-containing layers on alm.

The process is not limited to the coating of gelatino silver halideemulsion layers but can be used in drying other set or gelled colloidsilver halide emulsions and other types of layers, e. g., gelatinsublayers, gelatin filter layers, etc. Liquid layers of colloids whichgel or whose changes in viscosity lag or do not follow immediatelychanges in temperature, or whose melting point increases with holdingtime, can be dried as described above at such a rate that the coating isdry before it melts or is reduced in Viscosity sufiiciently tol flow. Aseries of coated sheets or plates, e. g., photographic plates on amoving belt can be dried in a manner similar to that described above.

This applicationis a continuation-impart of my copending applicationSer. No. 25,867, led May 8, 1948, now abandoned.

The invention has the advantage that it provides a practical commercialprocess for drying gelatin silver halide emulsion layers. A furtheradvantage is that it requires small size apparatus and buildings. Stillother advantages are: The lm is exposed for less time in moist conditionto contaminant dust. Less material is being processed at one time sothat smaller losses occur in the event of equipment failure. It obviatesthe need for long festoon driers, or tenter frames for supporting the lmor paper. By means of this invention it is possible to use air having ahigher moisture content than has been customary in the art. As a result,dehumidifying equipment can be much reduced and less expensive.

As many widely different embodiments of this invention can be madewithout departing from the spirit and scope thereof,v it is to beunderstood that the invention is not to be limited except as defined bythe claims.

What is claimed is:

1. The process which comprises coating an aqueous gelatino-silver halideemulsion onto a moving flexible web support, chilling the coated layerfrom 40 vto 75 F. to form a gelled emulsion layer, conditioning thegelled emulsion layer by passing the coatedweb through a zone maintainedat a temperature from 5'to 30 F. below the melting point of the emulsionfor a period of 10 to 180 seconds, then passing the coated web through adrying zone while exposing the emulsion layer to a high velocity currentof air maintained at a dry bulb temperature of 110 F. to 235 F., a wetbulb temperature of 68 F. to F. and an air velocity of 2000 to 15,000feet per minute so that the rate of evaporation from a free wet surfaceis 0.5 to 3.0 pounds per hour per sq. ft.

2. The process which lcomprises coating an aqueous gelatino-silverhalide emulsion onto a continuous, moving, exible, web support, chillingthe coated layer with air at a temperature from 40 F. to 70 F. to form agelled emulsion layer, conditioning the gelled emulsion layer by passingthe coated web through a zone maintained at a temperature from 5 to 30F. below the melting point of the emulsion for a period of 10 to 180seconds, then passing the coated web through a drying zone whileexposing the emulsion layer to ahigh velocity current of air having adry bulb temperature of F. to 235 F., a'wet bulb temperature of 68 F. to100 F. and an air velocity of V2000 to 15,000 feet per minute so thatthe emulsion is 2 F. to 20 F. above its normal melting point, andremoving said coated web from the drying zone after the moisture contenthas been reduced to 0.5 to 1.5 times the gelatin conltent of the coatedlayer.

3. The process which comprises coating an aqueous gelatine-silver halideemulsion onto a continuous, moving, flexible, paper sheet, chilling thecoated layer with air at a temperature from 40 F. to 70 F. to form agelled emulsion layer, conditioning the gelled emulsion layer by passingthe coated sheet through a zone maintained at a temperature from 5 to 30F. below the melting point of the emulsion for a period of to 180seconds, then passing the coated sheet through a drying zone whileexposing the emulsion layer to a high velocity current of air hav ing adry bulb temperature of 110 F. to 235 F., a wet bulb temperature of 68F. to 100 F. and an air velocity of 2000 to 15,000 feet per minute sothat the emulsion is 2 F. to 20 F. above its normal melting point, andremoving said coated sheet from the drying zone after the moisturecontent has been reduced to 0.5 to 1.5 times the gelatin consent of thecoated layer.

4. The process which comprises coating an aqueous gelatino-silver halideemulsion onto a continuous, moving, iiexible, hydrophobic lm, chillingthe coated layer with air at a temperature from 40 F. to '70 F. to forma gelled emulsion layer, conditioning the gelled emulsion layer bypassing the coated lm through a zone maintained at a temperature from 5to 30 F. below the melting point of the emulsion for a period of 10 to180 seconds, then passing the coated film through a drying Zone whileexposing the emulsion layer to a high velocity current of air having adry bulb temperature of 110 F. to 235 F., a Wet bulb temperature of 68F. to 100 F. and an air velocity of 2000 to 15,000 feet per minute sothat the emulsion is 2 F. to 20 F. above its normal melting point, andremoving said coated lm form the drying zone after the moisture contenthas been reduced to 0.5 to 1.5 times the gelatin content of the coatedlayer.

5. The process which comprises coating an aqueous gelatino-silver halideemulsion onto a continuous, moving, flexible, web support, chilling thecoated layer with air at a temperature from 40 F. to '70 F. to form agelled emulsion layer, conditioning the gelled emulsion layer by passingthe coated web through a zone maintained at a temperature from 5 to 30F. below the melting point of the emulsion for a period of 10 to 180seconds, then passing the coated web through a drying zone whileexposing said layer to a current of air having a velocity of 2,000 to15,000 feet per minute, a dry bulb temperature of 110 F. to 235 F. and awet bulb temperature 2 to 20 F. above the normal melting point of thegelled emulsion layer, for a period of 30 to 180 seconds.

6. The process which comprises coating an aqueous gelatine-silver halideemulsion onto a continuous, moving, exible web support, chilling thecoated layer with air at a temperature from 40 F. to '70 F. to form agelled emulsion layer, conditioning the gelled emulsion layer by passingthe coated web through a zone maintained at a temperature from 5 to 30F. below the melting point of the emulsion for a period of 10 to 180seconds, passing the conditioned web through a drying zone whileexposing said layer to a current of air having a velocity of 2,000 to15,000 feet per minute, a dry bulb temperature of 110 F. to 235 F. and awet bulb temperature 2 to 20 F. above the normal melting point of thegelled emulsion layer for a period of 30 to 180 seconds, then passingthe coated web into a curing zone while exposing the emulsion layer to acurrent of air having a velocity of to about 2,000 feet per minute, adry bulb temperature of '70 F. to 100 F., a wet bulb temperature from 50to '75 F. and a relative humidity of 30% to 60% so that the rate ofevaporation from a free wet surface will be less than 0.5 pound persquare foot per hour.

7. The process which comprises coating an aqueous gelatino-silver halideemulsion onto a continuous, moving, exible paper sheet, chilling thecoated layer with air at a temperature from 40 F. to '70 F. to form agelled emulsion layer, conditioning the gelled emulsion layer by passingthe coated sheet through a Zone maintained at a temperature from 5 to 30F. below the melting point of the emulsion for a period of 10 to 180seconds, passing the conditioned sheet through a drying zone whileexposing said layer to a current of air having a velocity of 2,000 to15,000 feet per minute, a dry bulb temperature of F. to 235 F. and a wetbulb temperature of 68 F. to 100 F. so that it is 2 to 20 F. above thenormal melting point of the gelled emulsion layer for a period of 30 to180 seconds, then passing the coated sheet into a curing Zone Whileexposing the emulsion layer to a current of air having a velocity of 40to about 2,000 feet per minute, a dry bulb temperature of 70 F. to 100F., a Wet bulb temperature from. 50 to r75" F. and a relative humidityof 30% to 60% so that the rate of evaporation from a free wet surfacewill be less than 0.5 pound per sq. ft. per hour.

8. The process which comprises coating an aqueous gelatina-silver halideemulsion onto a continuous, moving, flexible hydrophobic film, chillingthe coated layer with air at a tempera.- ture from 40 F. to '70 F. toform a gelled emulsion layer, conditioning the gelled emulsion layer bypassing the coated lm through a zone maintained at a temperature from 5to 30 F. below the melting point of the emulsion for a period of 10 to180 seconds, passing the conditioned film through a drying zone whileexposing said layer to a current of air having a velocity of 2,000 to15,000 feet per minute, a dry bulb temperature of 110 F. to 235 F. a wetbulb temperature of 68 F. to 100 F. so that it is 2 to 20 F. above thenormal melting point of the gelled emulsion layer for a period of 30 to180 seconds, then passing the coated lm into a curing zone whileexposing the emulsion layer to a current of air having a velocity of 40to about 2,000 4feet per minute, a dry bulb temperature of '70 F. to 100F., a Wet bulb temperature from 50 F. to '75 F. and a relative humidityof 30% to 60% so that the rate of evaporation from the free wet surfacewill be less than 0.5 pound per sq. ft. per hour.

CHESTER EUGENE ROSE.

No references cited.

1. THE PROCESS WHICH COMPRISES COATING AN AQUEOUS GELATINO-SILVER HALIDEEMULSION ONTO A MOVING FLEXIBLE WEB SUPPORT, CHILLING THE COATED LAYERFROM 40* TO 75* F. TO FORM A GELLED EMULSION LAYER, CONDITIONING THEGELLED EMULSION LAYER BY PASSING THE COATED WEB THROUGH A ZONEMAINTAINED AT A TEMPERATURE FROM 5* TO 30* F. BELOW THE MELTING POINT OFTHE EMULSION FOR A PERIOD OF 10 TO 180 SECONDS, THEN PASSING THE COATEDWEB THROUGH A DRYING ZONE WHILE EXPOSING THE EMULSION LAYER TO A HIGHVELOCITY CURRENT OF AIR MAINTAINED AT A DRY BULB TEMPERATURE OF 110* F.TO 235* F., A WET BULB TEMPERATURE OF 68* F. TO 100* F. AND AN AIRVELOCITY OF 2000 TO 15,000 FEET PER MINUTE SO THAT THE RATE OFEVAPORATION FROM A FREE WET SURFACE IS 0.5 TO 3.0 POUNDS PER HOUR PERSQ.FT.